Sensing the antisense: study of gene expression in differentiating leukemic
cells by a quantifying method
Ismini Karakasilioti
Leukemia is a type of cancer that develops in the blood-forming tissues of humans and other
animals and affects the development of immature blood cells into normal blood cells. As it
accounts for almost 8% of all cancers and affects mainly children around the age of ten, it has
been of major importance to understand the physiology of the disease, so as to be able to
introduce rewarding therapies.
Any cancerous cell, as well as a leukemic cell, differs from any normal cell in the way that it
has undergone many genetic changes. Such changes can be rearrangements of DNA
sequences throughout the genome, deletions or duplications of several parts of the
chromosomes and alteration in expression of several genes. Studies of these changes can
reveal the way the physiology of the cell changes when it becomes cancerous. In
consequence, they can evince new and important targets for cancer therapy.
During this project, the expression of a gene that is involved in regulation of cell growth was
studied. When treated with a certain drug, the leukemic cells changed from their cancerous
state towards a “normal” noncancerous state. This normalized state can be induced in vitro –
in cell cultures used in the lab and not in living patients – by treating the cancerous cells with
specific drugs, such as retinoic acid and 1,25-dihydroxy vitamin D3. This means that it would
be possible to view if and how the expression of a specific gene changes when the leukemic
cells became more normal. The aim was to monitor any possible differences in gene
expression in leukemic cells that were treated with this drug, compared to untreeated
leukemic cells.
More specifically, the level of gene expression that was studied was the regulation after the
DNA had been transcribed into RNA, by a reaction between sense and antisense transcripts
of the specific gene locus. The sense transcript is the RNA strand transcribed from the DNA
sequence of a gene that is later translated into a protein (mRNA). The antisense transcript is
the RNA strand that originates from the opposite DNA sequence of the same gene and, as a
consequence, is complementary to the first strand. If these two strands are simultaneously
present in a cell, they can bind to each other and noprotein will be made.
By a quantifying method, the abundance of these sense and antisense transcripts in leukemic
cells was examined. It was possible to see that this specific gene – Cyclin A – was
trasnccribed when the cells were leukemic. When normalized by the drug tratment, the cells
showed very low levels of Cyclin A expression. This was true for both sense and antisense
transcripts of the gene.
Degree project in biology, Autumn semester 2005
Examensarbete i biologi, 10p
Biology Education Centre and Department of Genetics and Pathology, Rudbeck Laboratory,
Uppsala University
Supervisor: Fredrik Öberg, Ph.D.